Multiphase flow (MPF) is simultaneous flow of materials with different states or phases (for example, gas, liquid, or solid), or materials with different chemical properties but in the same state or phase (for example, liquid-liquid systems such as oil droplets in water). MPF is a common phenomenon in the petroleum industry in the form of oil, water, gas, and other solvents. The behavior of MPF is much more complex than for single phase flow, and flow regime or flow pattern in MPF depends on a number of factors, including the relative density ratio of one fluid to the other, difference in viscosity between fluids, and velocity (for example, slip), of each respective fluid. The term “fluid flow” can include components like oil, water, gas, and solid (generally sand). An illustration of MPF can be seen in FIG. 7.
The oil and gas industry needs reliable meters to accurately measure MPF for a full range of water cut (for example, the volume of water produced compared to the total production volume). This ability to measure and characterize MPF, for example, into individual flow fractions, flow regimes, and water cut is significantly important in oil and gas operations. These characteristics are used in a variety of applications, including, for example, optimizing production, production monitoring, well testing, and water allocation. Oil-related operations can refer to any upstream or downstream production concerning hydrocarbons in any form, including, but not limited to, crude oil, natural gas, natural gas condensates, liquefied petroleum gas, heavy products, light products, and distillates.
There are several commercially available water cut and multiphase meters that use different measurement techniques, including microwaves, resonance, impedance, capacitance, conductance, gamma rays, and NIR. All of these meters, however, have shortcomings that affect, for example, the accuracy, safety, or cost of deploying the technique in the field. Capacitance and conductance based meters, for example, do no work in the phase inversion region when the flow changes its phase from oil-continuous to water-continuous or vice versa.
The meter using gamma rays is unsafe to handle due to its radioactivity. The only existing meter that uses NIR waves only measures a tiny volume of liquid that is not representative of the full MPF, and as a result, it produces large errors in low water cut measurements. Many of the techniques discussed are not suitable for downhole deployment due to frequent maintenance needs. No meter is available that can reliably measure water cut in the full range (0-100%) of oil, water, and gas fractions.
All of the proposed techniques are limited in measuring MPF of fluid over a complete range of liquid and gas flow rates. No water cut and MPF meter is commercially available that can accurately, reliably, and safely measure and characterize MPF of fluid in a full range of oil, water, and gas.